David Letterman says he will retire next year. He'll leave "The Late Show" as the longest-serving late night host in network television history, even longer than Johnny Carson when you add up Letterman's time at CBS, and NBC before that. NPR TV critic Eric Deggans says Letterman reshaped late night TV, and succeeded as an edgy outsider more interested in making fun of show business than participating in it.

ERIC DEGGANS, BYLINE: David Letterman has never had much patience for the trappings of the TV industry. So when he announced his retirement Thursday, he didn't have a press conference or highly planned media strategy. He just told his audience during a taping of his program, making sure to sprinkle lots of jokes around.

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DEGGANS: At age 66, Letterman is the oldest late night talk show host; during his announcement, he joked about hosting a late night show for half his life. Though Letterman didn't give a reason for his decision, CBS president Les Moonves noted in a statement the host signed a one-year contract extension last year, an indication he might step down soon. Neither CBS nor Letterman have set a date for his last show.

Born in Indianapolis, Letterman was a TV weatherman before he moved to Los Angeles and became a standup comic, impressing "Tonight Show" host Johnny Carson enough to become a regular guest host in the late 1970s. In 1982, after hosting a short-lived morning program, Letterman got his own late night show on NBC after Carson's program, called "Late Night."

It was here Letterman developed his signature style, poking fun at every aspect of conventional talk shows, and tangling with celebrities during interviews. But when Letterman was passed over as Carson's successor in 1992, he left NBC for CBS to lead a new program, called "The Late Show." He became a more mature broadcaster. And when the 9/11 attacks crippled New York City, Letterman returned days later with an emotional show.

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DEGGANS: Letterman has become the longest-serving late night host, with a 32-year career at two networks. Fellow late night hosts like Jimmy Kimmel and Conan O'Brien credit Letterman as an inspiration, showing a generation of performers how to succeed on TV with quirky, creative comedy.